MainStage Transpose software instrument channel strips
You can transpose (change the pitch of) a software instrument channel strip. When you transpose a channel strip, every MIDI note received by the channel strip is transposed by the number of semitones set in the Transpose value slider.
Transpose the MIDI input of a software instrument channel strip
Select the channel strip in the Channel Strips area.
In the MIDI Input tab of the Channel Strip Inspector, set the value using the Transpose value slider. You can click the value and drag up or down to set the value, click the up arrow or down arrow, or double-click the value and type a new value.